Radiation Therapy System, Radiation Therapy Method and Program

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-147800 filed on Aug. 29, 2024, the entire contents of which are incorporated herein by reference.

The present invention embodiment relates to a radiation therapy technique for treating patient's focus by using beam irradiation.

Radiation therapy is a treatment technique for destroying focuses (e.g., cancers) in patients via beam irradiation. Particle beams, such as carbon ion beams, may decay in kinetic energy when passing through the patient's body, and then particle beams would be rapidly stopped when velocity drops to a certain value. Particle beams form a dose of beam distribution referred to as the Bragg peak near the stop point thereof to release energy.

The irradiation condition and the patient's position should be determined such that a patient's focus will be positionally adjusted to the Bragg peak corresponding to the terminal position in the range of beams releasing energy. Thus, it is possible to realize treatment to maximize an absorbed dose of beams irradiated to focal tissues while keeping an absorbed dose of beams irradiated to normal tissues to a minimum.

For this reason, inaccurate positional adjustment of the Bragg peak to a patient's focus might result in a fear that normal tissues will be destroyed via beam irradiation. Therefore, treatment plans should be made before treatment administration for irradiating beams to patients. In the treatment plan, a CT scan is performed on a patient to obtain voxel data, thus three-dimensionally identifying the shape and the position of a patient's focus in the body. The setting position of a tabletop for fixing a patient's body, and the irradiation condition should be determined to apply an adequate dose of beams to focal tissues while reducing the dose of beams irradiated to normal tissues as small as possible.

It may take a certain time to determine the setting position of a tabletop, and the irradiation condition described above. In other words, it may generally take several days after a treatment plan before treatment administration. Internal organs such as a pancreas surrounded by digestive tracts in the body are characterized in that the position thereof in the body cannot be fixed to a certain position according to the amount of food ingested by a patient and the movement of a patient's body. The patient's focus appearing in any internal organ may be displaced in the body in each stage of treatment planning and treatment administration.

In this case, the interior of a patient's body shall be imaged even in the stage of treatment administration, thus observing a patient's focus displaced after the stage of treatment planning. The beam irradiation will be executed after correcting the setting position of the tabletop, and the irradiation condition based on the observed displacement of a patient's focus.

Patent Document 1 (Japanese Patent Application Publication No. 2023-172165) discloses a radiation therapy system simplifying the movement of a treatment table when acquiring 3D images. Patent Document 2 (Japanese Patent Application Publication No. 2019-147029) discloses a particle beam treatment system capable of accurately irradiating particle beams to the affected area of a patient regardless of a treatment plan. Patent Document 3 (Japanese Patent Application Publication No. 2016-209012) discloses a particle beam treatment system capable of accurately irradiating particle beams to the affected area of a patient regardless of a treatment plan.

The attenuation of beams passing through a patient's body is greatly influenced by the density of internal tissues and intestinal gas in the beam range. Thus, any discrepancy in terms of water equivalent lengths towards the patient's focus assumed in the stage of treatment planning may lead to any difference in the beam range inside a patient's body rather than the beam range assumed in an initial treatment plan.

The above discrepancy may bring the Bragg peak to be formed at a different position than the actual focal position imaged in the stage of treatment administration. Therefore, simply changing the setting position of a tabletop based on the positional displacement of patient's bones or focuses checked via an X-ray scan may lead to an insufficient dose of beams administered to focal tissues, which would possibly increase the dose of beams irradiated to normal tissues.

When correcting the irradiation condition to prevent an increasing dose of beams irradiated to normal tissues, it takes a long time for correction. This may impose a burden on a patient and increase the time of treatment.

The present invention embodiment is made in consideration of the above circumstances, and aims to provide a radiation therapy technique for maximizing an absorbed dose of beams irradiated to focal tissues in a short period of time while keeping an absorbed dose of beams irradiated to normal tissues to a minimum, even when the stage of treatment planning is affected by any change in the position of a patient's focus in the body or any change in the density of internal tissues or intestinal gas in the beam range.

According to the present invention embodiment, a radiation therapy system includes a hold unit configured to hold first movement information for moving a tabletop used to fix a patient's body thereon such that a first position of a patient's focus identified by first voxel data imaging the interior of the patient's body matches an isocenter in a dose of a beam administered to the patient's fucus, and the irradiation condition, which is set to maximize a focal coverage rate of a patient's focus irradiated with the beam at the first position; an identification unit configured to identify a second position of the patient's focus by second voxel data imaging the interior of the patient's body immediately before emitting the beam; and an update unit configured to update the first movement information with second movement information to maximize the focal coverage rate at the position of the patient's focus without changing the irradiation condition.

According to the present invention embodiment, a radiation therapy method includes the steps of: holding first movement information for moving a tabletop used to fix a patient's body thereon such that a first position of a patient's focus identified by first voxel data imaging the interior of the patient's body matches an isocenter in a dose of a beam administered to the patient's focus; holding an irradiation condition, which is set to maximize a focal coverage rate of the patient's focus irradiated with the beam at the first position; identifying a second position of the patient's focus by second voxel data imaging the interior of the patient's body immediately before emitting the beam; and updating the first movement information with second movement information to maximize the focal coverage rate at the position of the patient's focus without changing the irradiation condition.

According to the present invention embodiment, it is possible to maximize an absorbed dose of beams irradiated to focal tissues in a short period of time while keeping an absorbed dose of beams irradiated to normal tissues to a minimum, even when the stage of treatment planning is affected by any change in the position of a patient's focus in the body or any change in the density of internal tissues or intestinal gas in the beam range.

1 FIG. 10 13 14 10 13 36 14 13 25 26 20 14 11 13 31 35 Hereinafter, the present invention embodiments will be described with reference to the accompanying drawings.is a configuration diagram of a radiation therapy systemaccording to the first embodiment of the present invention. Treatment planningis carried out in advance prior to treatment administrationusing the radiation therapy system. The treatment planningis carried out in a different place than treatment chamberused to implement the treatment administration. In the treatment planning, a patientis fixed to a tabletopin the same posture as the posture to receive a beamirradiated thereto in the treatment administration, thus imaging first voxel data. Finally, the treatment planningwill produce first movement informationand irradiation condition.

11 13 25 The first voxel dataacquired in the stage of the treatment planningrepresents a three-dimensional image (or a stereoscopic image), imaging the interior body of the patient, which is obtained by stereoscopic imaging equipment, such as X-ray CT (Computed Tomography) or nuclear magnetic resonance (MRI: Magnetic Resonance Imaging).

31 26 25 21 15 15 11 25 16 20 15 a a. The first movement informationis data for moving the tabletopused to fix the patientthereon such that a first positionof a focus(), which is identified by the first voxel dataimaging the interior body of the patient, matches an isocenterof the beamfor administering a dose of beams to the focus

19 19 21 15 11 a An identification unit() is configured to identify the first positionof the focusdistinct from normal tissues in a coordinate system referring to an area showing no positional displacement of bones in the first voxel dataor a reference position of imaging equipment.

17 26 36 13 17 31 26 21 15 16 20 a A generation unithas a function of generating movement information input to a transport mechanism (not shown) for positioning the tabletopin the treatment chamber. In the stage of the treatment planning, the generation unitgenerates the first movement informationas a command given to the transport mechanism (not shown) for positioning the tabletopsuch that the first positionof the focusmatches the isocenterof the beam.

26 36 17 21 11 36 31 21 16 36 The transport mechanism (not shown) has a unique function to adjust the position and the orientation of the tabletopin a coordinate system referring to the treatment chamber. The generation unitis configured to convert the first positiondefined in the coordinate system of the first voxel datato the coordinate system of the treatment chamber, thereby generating the first movement informationsuch that the first positionmatches the isocenteroriginally defined in the coordinate system of the treatment chamber.

18 35 20 15 13 35 56 25 20 21 56 15 a 4 4 FIGS.A toC An adjustment unitis configured to adjust the irradiation conditionof the beamirradiated to the focus, such as a dose of irradiation, an irradiation angle, an irradiation range, and the number of times for irradiating beams. In the treatment planning, the irradiation conditionis set to maximize a focal coverage rate(see) of the patientirradiated with the beamat the first position. The focal coverage raterefers to a focal coverage rate of the focusreceiving a prescribed dose of irradiation.

10 14 30 35 20 31 26 19 19 22 15 12 25 20 50 31 32 56 15 25 35 b The radiation therapy systemin use of the operation of the treatment administrationincludes a holding unitconfigured to hold the irradiation conditionof the beamand the first movement informationof the tabletop, an identification unit() configured to identify a second positionof the focusby second voxel dataimaging the interior body of the patientimmediately before irradiation of the beam, and an update unitconfigured to update the first movement informationwith second movement informationsuch that the focal coverage ratewill be maximized at the position of the focusof the patientwithout changing the irradiation condition.

2 FIG. 16 28 10 27 20 28 10 27 28 20 15 15 15 25 26 27 25 20 15 15 a b is an explanatory schematic of a rotational motion about the isocenterof a rotating gantryin the radiation therapy systemaccording to the first embodiment of the present invention. An irradiation portused to irradiate the beamis fixed to the rotating gantryof the radiation therapy system. Since the irradiation portrotates about a rotation axis together with the rotating gantry, it is possible to irradiate the beamto the focus(,) of the patientin an arbitrary direction without tilting the tabletop. By rotating the irradiation portaround the body axis of the patientin this way, it is possible to irradiate the beamto the focusin multiple directions, thus suppressing the dose of beams irradiated to normal tissues around the focusto a minimum.

28 37 36 38 28 28 28 37 The rotating gantrygenerally constituted of a large-size structure having a cylindrical shape is designed to rotate about the rotation axis by rotationally driving a plurality of rotation drive partscircumscribed on the outer circumference at both edges thereof. The treatment chamberis formed inside a moving platform, which is disposed along the inner circumference of the rotating gantryand circumferentially rotates with the rotation of the rotating gantry. The weight of the rotating gantryis supported by a stationary system (not shown) via the rotation drive parts.

27 28 20 20 20 27 16 28 In addition to the irradiation port, the rotating gantryis equipped with a plurality of beam transport ducts, beam deflection magnets, and other control devices and structures, the illustrations of which re omitted here. The beamis generated by accelerating ions (heavy particles or proton ions) produced by an ion source by a linear accelerator whose illustration is omitted here, and injecting ions into a circular accelerator (not shown) to raise the energy of ions to the preset energy level. The beampicked up from the circular accelerator is transported by a beam transport system (not shown), and then the beamis irradiated from the irradiation portto the isocenterdisposed on the rotation axis of the rotating gantry.

1 FIG. 10 23 24 28 16 24 29 Returning to, the radiation therapy systemis equipped with stereoscopic imaging equipment including two pairs of an X-ray tubeand an X-ray detector, which is installed in the rotating gantrysuch that two pairs mutually intersect by an angle of 90 degrees with respect to the isocenter. The X-ray detectorarranges a two-dimensional array of detection elements used to detect an X-ray.

45 29 23 16 24 29 25 45 25 45 48 28 An imaging unitirradiates the X-rayfrom the X-ray tubeto the isocenter. The X-ray detectoris configured to detect the X-raypassing through the patientvia the detection elements based on an attenuation of energy such that the imaging unitcan receive a two-dimensional perspective image of the patient. The imaging unitinstructs a rotation control unitto rotate the rotating gantryin at least a quarter rotation.

45 12 25 45 12 23 24 16 28 The imaging unitis configured to produce the second voxel dataupon acquiring a plurality of two-dimensional perspective images capturing the patientin different directions. In this way, the imaging unitcaptures the second voxel databy rotating combinations of the X-ray tubeand the X-ray detectorabout the isocenterand in synchronization with the rotating gantry.

23 24 28 23 24 28 28 In this connection, the present embodiment exemplifies the integral structure including the X-ray tubeand the X-ray detectorintegrally unified with the rotating gantry, but it is possible to adopt another structure and control which can rotate the X-ray tubeand the X-ray detectorwithout being synchronized with the rotating gantry. In this case, it is expected to increase the speed of the operation since the rotating gantryas a large-size structure does not need to rotate by itself.

19 19 22 15 12 19 19 14 19 19 13 11 12 b b b a The identification unit() is configured to identify the second positionof the focusdistinct from normal tissues in a coordinate system referring to an area having no positional displacement of patient's bones or a reference position of imaging equipment in the second voxel data. Therefore, the identification unit() used in the treatment administrationhas the same function as the identification unit() used in the treatment planning. That is, it is possible to express both the first voxel dataand the second voxel datain the common coordinate system.

30 35 20 31 26 13 35 50 31 32 56 15 25 46 26 25 36 32 The holding sectionis configured to hold, as initial settings, the irradiation conditionof the beamand the first movement informationof the tabletop, which are set in the treatment planning. Without changing the irradiation condition, the update unitupdates the first movement informationwith the second movement informationsuch that the focal coverage ratewill be maximized at the focal position of the focusof the patient. A setting unitis configured to set the tabletopfor fixing the patientthereon to the coordinate system of the treatment chamberbased on the updated second movement information.

26 32 48 28 35 13 47 20 25 35 After setting the tabletopbased on the second movement information, the rotation control unitdisplaces the rotating gantryin rotation based on the irradiation conditionset in the treatment planning. Then, an irradiation unitirradiates the beamto the patientbased on the irradiation condition.

20 27 20 28 16 27 36 The beamis a type of radiation irradiated to focal tissues such as cancer to kill cells. As such a type of radiation, it is possible to mention X-rays, y-rays, electron beams, proton beams, and heavy particle beams. The present embodiment refers to the installation of the irradiation portof the beaminstalled in the rotating gantryrotating about the isocenter, but this is not a limitation. For example, it is possible to adopt the fixation of the irradiation portfixed to the treatment chamber.

26 25 45 12 11 13 45 12 45 16 36 For accurately positioning the tabletopused to fix the patientthereon, the imaging unitfor the second voxel datamay originally exemplify the usage of the function of capturing a two-dimensional perspective image to be cross-checked with the DDR (Digitally Reconstructed Radiograph) reconstructing the first voxel dataused in the treatment planning. However, this is not a limitation to the imaging unitfor the second voxel data. For example, the imaging unitmay be general-purpose medical stereoscopic imaging equipment, such as an X-ray CT or MRI equipment, which is installed separately at a position away from the isocenterinside or outside of the treatment chamber.

1 FIG. 3 FIG. 3 FIG. 50 10 10 50 Next, the second embodiment of the present invention will be described with reference toand.is a configuration diagram of the update unitof the radiation therapy systemaccording to the second embodiment. The radiation therapy systemof the second embodiment is characterized by the configuration of the update unitamong configurations in the first embodiment described above.

50 53 40 25 20 52 22 35 55 56 15 40 57 52 58 56 41 51 58 21 59 51 31 32 The update unitin the second embodiment includes a calculation unitconfigured to calculate a dose distributionfor the patientwhen the beamis irradiated to a plurality of temporary positionsin the peripheral region covering the second positionunder the irradiation condition, a derivation unitconfigured to derive the focal coverage rateat the focal position of the focusfor a plurality of dose distributions, a selection unitconfigured to select from among a plurality of temporary positionsa selected positionat which the focal coverage ratehas a maximum value, a computation unitconfigured to produce a difference vectorrepresenting a difference between the selected positionand the first position, and an addition unitconfigured to add the difference vectorto the first movement informationand to thereby produce the second movement information.

42 52 22 12 42 52 22 12 12 52 22 12 A temporary setting unitconfigured to temporarily set a plurality of temporary positionsassumed in the peripheral region covering the second positionin the coordinate system of the second voxel data. That is, the temporary setting unitis configured to temporarily set a plurality of temporary positionsin the peripheral region covering the second positionidentified by the second voxel dataaccording to the coordinate system of the second voxel data. Thus, it is possible to provide a plurality of temporary positionsabout the second positionat regular intervals in the coordinate system of the second voxel data.

4 FIG.A 4 FIG.B 4 FIG.C 40 20 15 21 11 13 40 20 15 22 12 14 40 20 15 58 56 16 a a b b c is a graph showing a dose distributionin the propagating direction of the beamirradiated to the focusat the first positionof the first voxel dataimaged in the stage of the treatment planning.is a graph showing a dose distributionin the propagating direction of the beamirradiated to the focusat the second positionof the second voxel dataimaged in the stage of the treatment administration.is a graph showing a dose distributionin the propagating direction of the beamirradiated to the focusat the selected position, which is selected such that the focal coverage ratewill have a maximum value by updating the position of the isocenter.

53 40 25 20 16 22 35 13 55 56 15 40 b b b. 4 FIG.B The calculation unitis configured to calculate the dose distribution(see) in the interior body of the patientwhen the beamis irradiated to the isocenterat the second positionunder the irradiation conditionsset in the treatment planning. The derivation unitis configured to derive a focal coverage rateof the focusfor the dose distribution

53 40 25 20 52 35 13 55 56 15 40 57 52 22 58 56 c 4 FIG.C Similarly, the calculation unitis configured to calculate the dose distributionin the interior body of the patientwhen the beamis irradiated to a plurality of temporary positionsunder the irradiation conditionset in the treatment planning. The derivation unitis configured to derive the focal coverage rateof the focusfor a plurality of dose distributions. The selection unitis configured to select from among a plurality of temporary positionsincluding the second position, the selected positionat which a focal coverage rate(see) has a maximum value.

3 FIG. 41 51 15 11 12 13 14 59 51 31 32 15 14 36 Returning to, the computation unitproduces the difference vectorcorresponding to the distance and the direction in which the focushas been displaced in the first voxel dataor the second voxel dataduring the period counted from the stage of the treatment planningto the stage of the treatment administration. The addition unitadds the difference vectorto the first movement informationto produce the second movement informationcorresponding to the position of the focusin the stage of the treatment administrationin the coordinate system of the treatment chamber.

46 16 58 15 25 26 32 20 25 32 56 16 21 56 16 58 56 58 56 21 1 FIG. 4 FIG.A 4 FIG.C a c c a The setting unit(see) is configured to match the isocenterwith the selected positionof the focusof the patientby setting the position of the tabletopbased on the second movement information. In this connection, it is necessary to determine the validity of irradiating the beamto the patientwith respect to the second movement informationupdated in this way. It is possible to determine the validity based on a ratio of the focal coverage rate(), which is produced when the isocenteris forced to match the first position, to the focal coverage rate(), which is produced when the isocenteris forced to match the selected position. Specifically, it is ideal that the ratio between the focal coverage rateat the selected positionand the focal coverage rateat the first positionwould be 100%.

50 31 32 51 31 32 The update unitin the second embodiment is configured to update the first movement informationwith the second movement informationby using the difference vector, but this is not a limitation. As another example of configuration, it is possible to think out a configuration for updating the first movement informationwith the second movement informationby adopting optimization of hexa-degree freedom.

5 5 FIGS.A andB 5 FIG.A 13 13 11 25 11 21 15 11 12 The procedure of a radiation therapy method and the algorithm of a radiation therapy program according to the present invention embodiment will be described with reference to the flowcharts of.shows the procedure related to the treatment planning. In the stage of the treatment planning, the medical stereoscopic imaging equipment (e.g., X-ray CT or MRI equipment) is used to image the first voxel datarepresentative of the interior body of the patient(S). Subsequently, the first positionof the focusis identified from the first voxel data(S).

31 26 16 21 13 35 20 56 25 20 21 14 a 5 FIG.A Next, the first movement informationfor moving the tabletopis generated such that the isocentermatches the first position(S). In addition, the irradiation conditionof the beamis set such that the focal coverage rateof the patientirradiated with the beamis maximized at the first position(S). Thus, the flow ofhas ended.

5 FIG.B 14 14 31 35 13 15 12 25 20 16 22 15 12 17 shows the procedure related to the treatment administration. In the stage of the treatment administration, the first movement informationand the irradiation conditionset in the treatment planningare held (S). Subsequently, the second voxel datarepresenting the interior body of the patientis captured immediately before irradiating the beam(S). In addition, the second positionof the focusis identified from the second voxel data(S).

40 15 25 35 18 56 15 32 19 31 32 20 Next, the dose distributionat the position of the focusof the patientis calculated without changing the irradiation condition(S). When the focal coverage rateat the position of the focusaccording to the second movement informationindicates a maximum value (S, Yes), the first movement informationis updated with the second movement information(S).

26 32 21 35 20 25 22 5 FIG.B Next, the position of the tabletopis adjusted based on the second movement information(S). Based on the irradiation condition, the beamis irradiated to the patient(S). Thus, the flow inhas ended.

10 26 56 15 20 35 13 35 35 According to the radiation therapy systemof the foregoing embodiments in which the movement information of the tabletopis updated to maximize the focal coverage rateat the position of the focusimmediately before irradiating the beam, it is possible to maximize the absorbed dose of beams in focal tissues while keeping the absorbed dose of beams in normal tissues to a minimum, without changing the irradiation conditions, irrespective of any displacement of the position of the focus in the body occurring after the stage of the treatment planning. This may preclude the necessity of changing the irradiation conditionwhile reducing the time required to correct the irradiation condition, which may realize high-accuracy and short-time treatment, thus contributing to a reduction of burden on a patient and an improvement of treatment throughput.

Although several embodiments of the present invention have been described heretofore, the embodiments are illustrative and not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and therefore various omissions, substitutions, modifications, and combinations can be made without departing from the gist of the invention. The embodiments and modifications shall be included within the scope and the gist of the invention as well as within the scope of the invention as defined in claims and equivalents thereof.

The radiation therapy system described above includes a control device having a highly integrated processor such as a specified chip, a FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), or a CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) and RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) and SSD (Solid State Drive), a display device such as a display, an input device such as a mouse and a keyboard, and a communication interface (I/F), wherein the radiation therapy system can be realized by a hardware configuration using a generally-used computer. Therefore, the constituent elements of the radiation therapy system can be realized by a computer processor working on a radiation therapy program.

It is possible to provide the radiation therapy program incorporated in memory such as ROM in advance. Alternatively, it is possible to provide the radiation therapy program as files having the installable or executable format stored on a non-transitory computer-readable storage medium such as CD-ROM, CD-R, a memory card, DVD, and a flexible disk (FD).

The radiation therapy program according to the present embodiment may be stored on a computer connected to networks such as the Internet such that the radiation therapy program can be provided and downloaded through networks. The radiation therapy system can be established using individual modules capable of achieving the functions of constituent elements individually, which are combined and mutually connected to networks or private lines.

10 radiation therapy system 11 first voxel data 12 second voxel data 13 treatment planning 14 treatment administration 15 15 a b (,) focus 16 isocenter 17 generation unit 18 adjustment unit 19 19 19 a b (,) identification unit 20 beam 21 first position 22 second position 23 X-ray tube 24 X-ray detector 25 patient 26 tabletop 27 irradiation port 28 rotating gantry 29 X-ray 30 hold unit 31 first movement information 32 second movement information 35 irradiation conditions 36 treatment chamber 37 rotation drive unit 38 moving platform 40 40 40 40 a b c (,,) dose distribution 41 computation unit 42 temporary setting unit 45 imaging unit 46 setting unit 47 irradiation unit 48 rotation control unit 50 update unit 51 difference vector 52 temporary position 53 calculation unit 55 derivation unit 56 56 56 56 a b c (,,) focal coverage rate 57 selection unit 58 selected position 59 addition unit